1. Field of the Invention
The present invention relates to a laminated ceramic electronic component and its manufacturing method, and more particularly, relates to a laminated ceramic electronic component in which an external electrode is formed on an outer surface of a component main body by directly carrying out a plating process thereon, and a manufacturing method thereof.
2. Description of the Related Art
There have been demands for miniaturizing the size of a laminated ceramic electronic component, such as a laminated ceramic capacitor. For example, in the laminated ceramic capacitor, when the component main body is miniaturized in an attempt to satisfy the demands for small size, in general, its electrostatic capacity becomes smaller. Therefore, it is proposed to make the volume of the electrode smaller as a measure that can satisfy the demands for small size.
Conventionally, the external electrode generally has a layer structure in which, on a thick-film layer that is formed by baking a conductive paste formed thereon by a dipping method as an undercoat layer, a plated film is formed. In this case, if the thick film layer to be formed by the baking process of the conductive paste is omitted so that the external electrode can be formed by using only the plated film, the thickness of the external electrode can be made much thinner. Therefore, the miniaturization of the laminated ceramic capacitor is successfully achieved accordingly, or the corresponding saved space can be used for the capacity formation portion in the component main body.
For example, JP-A No. 2005-340663 has proposed a laminated ceramic capacitor in which the external electrode is formed only by the plated film as described above. JP-A No. 2005-340663 has proposed a structure in which, so as to connect exposed portions of a plurality of inner electrodes on an end surface of a component main body, a plated film is directly formed on the end surface by using an electroless plating process so that the external electrode is formed. Moreover, in JP-A No. 2005-340663, in order to form the external electrode so as to wrap around one portion of each of two main surfaces that are adjacent to each other on the end surfaces of the component main body, dummy electrodes are formed by using the same formation method as that of the inner electrode, and the dummy electrodes are also exposed to the main surface sides of the component main body.
In the laminated ceramic capacitor described in JP-A No. 2005-340663, however, moisture tends to invade along an interface between the plated external electrode and the component main body to cause a problem in which the insulating resistance is lowered. In particular, it is found that the invasion of moisture from the tip portion of the external electrode positioned on each of two main surfaces of the component main body becomes conspicuous.
In order to solve this problem, JP-A No. 2008-41786 has proposed a structure in which, in the external electrode, a dummy electrode containing glass frit is formed between a wraparound portion on one portion of each of the main surfaces of the component main body and the component main body with a baking process.
In accordance with the structure described in JP-A No. 2008-41786, since the gap between the wraparound portion of the main surface of the external electrode and the component main body is filled with the glass frit contained in the dummy electrode, it is possible to prevent moisture from invading into the gap. Therefore, it becomes possible to suppress degradation of the insulating resistance of a laminated ceramic electronic component, such as a laminated ceramic capacitor, and consequently to improve the moisture load resistant property.
Upon adopting the structure described in JP-A No. 2008-41786, floated glass tends to occur on the surface of the dummy electrode, and when such floated glass occurs, the plated film to form the external electrode tends to fail to be deposited in a preferable state. Moreover, depending on the kinds of plating liquids, the floated glass is fused to allow the plating liquid to invade into the dummy electrode. These problems give adverse effects to the reliability of the laminated ceramic electronic component.